trouble is, lying is really quite difficult for autistic folk... it's not a defining characteristic, but it does seem to be relatively common
what might work better is someone compiling a database of logins for free wifi, so that if you go to the mall you can just check the database, grab a login nobody's using, and put it back on the peg when you leave. an app could help with this, by automatically doing that when the wifi connection goes away - and automatically creating a new login where none are available using fictional details
...i might be overthinking this ;-)